It is not hard to write one. I have done many for clients. Google maps has an easy to use API. You basically have your developers create a new HTML page and then embed the map on the page. If you need to get access to any data to overlay on the map, use PHP to gain access.

Why do you think you require a new module? I can be reached at duane at nickull dot net if you want to discuss.

Drupal has two modules that can work together to integrate with Google Maps:
https://drupal.org/project/gmap implements the Google Maps API within Drupalhttps://drupal.org/project/location stores location data within a Drupal node
There's a few other modules that extend the functionality of these two, such as Geofield (https://drupal.org/project/geofield) and OpenLayers (https://drupal.org/project/openlayers).